The article by K. Aminian et al. entitled “Spatio-temporal parameters of gait measured by an ambulatory system using miniature gyroscopes”, Journal of Biomechanics 35 (2000), pages 689-699, describes a method of analyzing gait that makes use of at least one gyroscope fastened to a person's “shank” or tibial segment. A comparison with signals acquired by pressure-sensitive switches fastened to the heel and to the big toe shows that measuring the angular velocity of the tibial segment, as performed by means of a gyroscope, makes it possible to identify two characteristic instants of the swing: the moment when the toe leaves the ground (TO, for “toe-off”), and the moment when the heel strikes the ground (HS, for “heel-strike”). The period lying between the instants TO and HS corresponds to the flight phase of the swing for the leg under consideration; conversely, the period extending between the instants HS and TO corresponds to the support phase.
The drawback of the device proposed by K. Aminian et al. is associated with using gyroscopes, which are devices that are relatively bulky (and therefore uncomfortable for the person) and that consume a large amount of electricity.
The use of pressure-sensitive switches, also disclosed in the above-mentioned article, gives information only about the support phase and not about the flight phase of the swing.
Document EP 1 721 573 describes a method of estimating the phase of the movement of an object, which method includes acquiring experimental data from measuring physical magnitudes by means of at least one sensor. In particular, that document mentions determining the heel strike (HS instant) by analyzing an acceleration signal. The main drawback of that method is its computational complexity. Furthermore, accelerometers are sensitive to the inseparable combination of acceleration due to gravity and acceleration of the sensor. This presents high frequency components that make it difficult to determine the direction of acceleration due to gravity.
The article by S. Bonnet and R. Héliot entitled “A magnetometer-based approach for studying human movements”, published in IEEE Transactions on Biomedical Engineering, Vol. 54, No. 7, July 2007, pages 1353-1355, describes a method making it possible to study the inclination of the torso with the help of magnetometers. In particular, by assuming that motion is planar, it is possible to determine the angle formed by the torso relative to the vertical. Nevertheless, the processing of the data is complex (minimizing a cost function relative to two variables). In addition, the document does not give any indication on how it might be possible to use the information as obtained in that way to identify instants and phases that are characteristic of a person's gait.
Document FR 2 895 499 describes a method of measuring the orientation of a solid with the help of a magnetometer, and also an application thereof to determining the orientation of the thigh and the tibia of a leg while walking, from which it is possible to deduce the angle of the knee. Identifying instants and/or phases that are characteristic of gait is neither described nor suggested.
The article by R. Héliot et al. entitled “Continuous identification of gait phase for robotics and rehabilitation using microsensors”, published in Proceedings of the International Conference on Advanced Robotics, 2005—ICAR '05, describes a method of determining gait phases from orientation measurements of the tibia and of the thigh performed with the help of respective sensors, comprising accelerometers and magnetometers, which method requires complex data processing.